SimpleXML is an 'Object Mapping XML API'. It is not DOM, per se. SimpleXML converts the XML elements into PHP's native data types.

The dom_import_simplexml and simplexml_import_dom functions do *not* create separate copies of the original object. You are free to use the methods of either or both interchangeably, since the underlying instance is the same.

What this illustrates is that both interfaces are operating on the same underlying object instance. Also, when you dom_import_simplexml, you can create and add new elements without reference to an ownerDocument (or documentElement).

So passing a SimpleXMLElement to another method does not mean the recipient is limited to using SimpleXML methods.

I've found that newer versions of PHP5 require some special syntax in order to properly convert between SimpleXML and DOM. It's not as easy as calling dom_import_simplexml() with a SimpleXML node. To get a proper DOM document (which you need to do most things) you need:<?php//$xml is a SimpleXML instance$domnode = dom_import_simplexml($xml);$dom = new DOMDocument();$domnode = $dom->importNode($domnode, true);$dom->appendChild($domnode);?>